After updates of the main program, updating of your wiki language plugin may be necessary to reflect changes in the default language plugin. At the beginning of the original "WikidPadParser.py" there is a comment "# Last modified ..." telling you the date of last modification of this file

WikidPad's parser is based on pyparsing (but modified in some ways). For deeper understanding of the language grammar, you should therefore also look at ​http://pyparsing.wikispaces.com/